SPECIFIC AIMS Insulin Dependent Diabetes (Type 1) is a disease caused by the destruction of the insulin-producing beta cell of the pancreas. In the vast majority of patients this destruction is caused by a T cell mediated autoimmune process. Evidence for this is the association of Type 1 Diabetes with certain human leukocyte antigen (HLA) types and the presence of islet cell and antigen specific antibodies in the serum of newly diagnosed patients. The presence of these genetic markers and of various autoantibodies in the serum of these patients and their families have been instrumental in predicting with a high degree of certainty those individuals at high risk for developing diabetes. Puerto Rico has the highest incidence of Type 1 diabetes in children less than 15 years of age among Latin American countries with the same ethnic background: 18/100,000. (1) There is scant data on the presence of these genetic markers and of the presence of islet cell antibodies in the sera of Puerto Rican children and their families. The goal of this study is to characterize the Puerto Rican patient with Type 1 diabetes and his family. We plan to fulfill this goal by meeting the following objectives: 1.Determine the HLA type of recently diagnosed diabetics and to correlate it to their autoimmune profile. 2. To detect the presence of anti Islet Cell Antibodies (ICA) on the sera of newly diagnosed diabetics. 3. To detect the presence of Glutamic Acid Decarboxylase (GAD 65), Insulin Autoantibodies (IAA), and Protein tyrosine phosphatase (Ia-2) on the sera of newly diagnosed diabetics and their families. 4. To correlate the age of diagnosis and residual insulin secretion with the autoimmune profile of the diabetic. 5. To detect how long do antibodies persist after diagnosis.